Low motion to photon latency rapid target acquisition

ABSTRACT

Techniques for updating a position of overlaid image content using IMU data to reflect subsequent changes in camera positions to minimize latency effects are disclosed. A “system camera” refers to an integrated camera that is a part of an HMD. An “external camera” is a camera that is separated from the HMD. The system camera and the external camera generate images. These images are overlaid on one another and aligned to form an overlaid image. Content from the external camera image is surrounded by a bounding element in the overlaid image. IMU data associated with both the system camera and the external camera is obtained. Based on that IMU data, an amount of movement that the system camera and/or the external camera have moved since the images were originally generated is determined. Based on that movement, the bounding element is shifted to a new position in the overlaid image.

BACKGROUND

Mixed-reality (MR) systems, including virtual-reality (VR) andaugmented-reality (AR) systems, have received significant attentionbecause of their ability to create truly unique experiences for theirusers. For reference, conventional VR systems create completelyimmersive experiences by restricting their users' views to only virtualenvironments. This is often achieved through the use of a head-mounteddevice (HMD) that completely blocks any view of the real world. As aresult, a user is entirely immersed within the virtual environment. Incontrast, conventional AR systems create an augmented-reality experienceby visually presenting virtual objects that are placed in or thatinteract with the real world.

As used herein, VR and AR systems are described and referencedinterchangeably. Unless stated otherwise, the descriptions herein applyequally to all types of MR systems, which (as detailed above) include ARsystems, VR reality systems, and/or any other similar system capable ofdisplaying virtual content.

A MR system may also employ different types of cameras in order todisplay content to users, such as in the form of a passthrough image. Apassthrough image or view can aid users in avoiding disorientationand/or safety hazards when transitioning into and/or navigating within aMR environment. A MR system can present views captured by cameras in avariety of ways. The process of using images captured by world-facingcameras to provide views of a real-world environment creates manychallenges, however.

Some of these challenges occur when attempting to align image contentfrom multiple cameras, such as an integrated “system camera” and adetached “external camera” when generating the passthrough image.Challenges also occur when additional visualizations are provided in theresulting overlaid passthrough image, where these visualizations aredesigned to indicate a spatial relationship between the system cameraand the external camera. The time taken to i) generate a system cameraimage and an external camera image, ii) overlay and align the content,and then iii) display the resulting overlaid passthrough image withadditional visualizations is not instantaneous. Because of that,movement of the system camera and/or the external camera may occurbetween the time when the images are generated and when the finalpassthrough image is displayed. Such movement results in a visiblelatency or lagging effect and is disruptive to the user. Aligning imagecontent provides substantial benefits, especially in terms of hologramplacement and generation, so these problems present serious obstacles tothe technical field. Accordingly, there is a substantial need in thefield to improve how images are aligned with one another.

The subject matter claimed herein is not limited to embodiments thatsolve any disadvantages or that operate only in environments such asthose described above. Rather, this background is only provided toillustrate one exemplary technology area where some embodimentsdescribed herein may be practiced.

BRIEF SUMMARY

Embodiments disclosed herein relate to systems, devices (e.g., wearabledevices, hardware storage devices, etc.), and methods that update aposition of overlaid image content using inertial measurement unit (IMU)data to reflect subsequent changes in camera positions in order tominimize latency effects.

In some embodiments, a system camera of a head-mounted mixed-realitysystem is used to generate a system camera image of an environment inwhich the system is operating. Additionally, the embodiments cause anexternal camera to generate an external camera image of the environment.The embodiments generate an overlaid image by overlaying and aligning atleast some of the content included in the external camera image on topof corresponding content included in the system camera image. Notably,at least some of the external camera image's content is surrounded by abounding element in the overlaid image. The embodiments obtain systemIMU data from an IMU of the system and also obtain external IMU datafrom an IMU of the external camera. Based on the system IMU data and theexternal IMU data, the embodiments determine an amount of movement thatthe system camera and/or the external camera have moved relative to oneanother since a time when the system camera image and the externalcamera image were generated. Based on the determined amount of movement,the embodiments shift the bounding element to a new position in theoverlaid image such that the shifted bounding element reflects anupdated positional relationship between a field of view (FOV) of thesystem camera and a FOV of the external camera since the time when thesystem camera image and the external camera image were generated.

Some embodiments predict where a bounding element is to be locatedwithin an overlaid image using IMU data in order to minimize, or eveneliminate, latency effects. For example, after the external IMU data isobtained from the IMU of the external camera in the manner describedabove, some embodiments perform the following operations (as opposed toperforming the last two operations mentioned above). In particular, someembodiments generate (e.g., based on the system IMU data and theexternal IMU data) a prediction indicating a predicted relative positionthat the external camera will be relative to the system camera at adetermined future point in time. Based on that prediction, theembodiments shift the bounding element to a new position in the overlaidimage in order to reflect the predicted relative position of theexternal camera relative to the system camera. The resulting overlaidimage with the updated bounding element is a type of passthrough image,which may be displayed to the user.

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used as an aid in determining the scope of the claimed subjectmatter.

Additional features and advantages will be set forth in the descriptionwhich follows, and in part will be obvious from the description, or maybe learned by the practice of the teachings herein. Features andadvantages of the invention may be realized and obtained by means of theinstruments and combinations particularly pointed out in the appendedclaims. Features of the present invention will become more fullyapparent from the following description and appended claims or may belearned by the practice of the invention as set forth hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to describe the manner in which the above-recited and otheradvantages and features can be obtained, a more particular descriptionof the subject matter briefly described above will be rendered byreference to specific embodiments which are illustrated in the appendeddrawings. Understanding that these drawings depict only typicalembodiments and are not therefore to be considered to be limiting inscope, embodiments will be described and explained with additionalspecificity and detail through the use of the accompanying drawings inwhich:

FIG. 1 illustrates an example head-mounted device (HMD) configured toperform the disclosed operations.

FIG. 2 illustrates another configuration of an HMD.

FIG. 3 illustrates an example scenario in which the disclosed principlesmay be practiced.

FIG. 4 illustrates another example scenario.

FIG. 5 illustrates how a system camera and an external camera can beused to perform the disclosed operations.

FIG. 6 illustrates the field of view (FOV) of a system camera.

FIG. 7 illustrates the FOV of an external camera.

FIG. 8 illustrates an overlaid and aligned image in which image contentfrom the external camera is overlaid onto the system image.

FIG. 9 illustrates another example scenario in which the principles maybe practiced.

FIG. 10 illustrates how an external camera image can be overlaid onto asystem camera image.

FIG. 11 illustrates how movement of either the system camera or theexternal camera can cause latency in the resulting overlaid image.

FIG. 12 illustrates an example of the lagging or latency effect.

FIG. 13 illustrates a technique for shifting a bounding element in aneffort to minimize the effects of latency.

FIGS. 14A and 14B illustrate a flowchart of an example method forminimizing the effects of latency.

FIG. 15 illustrates various features of an overlaid image.

FIG. 16 illustrates how pixel data from the system camera image can beexposed or used to fill in certain areas within a bounding element.

FIG. 17 illustrates how an original alignment between the externalcamera image and the system camera image is preserved.

FIG. 18 illustrates how a bounding element can encompass pixels havingdifferent levels of resolution.

FIG. 19 illustrates how a bounding element can encompass pixels obtainedonly from a system camera image.

FIG. 20 illustrates the effects of different types of movement.

FIG. 21 illustrates an example timeline detailing some of the timingrelationships between different events.

FIG. 22 illustrates a flowchart of an example method for predictingwhere a bounding element should be located at some future point in time.

FIG. 23 illustrates an example computer system.

DETAILED DESCRIPTION

Embodiments disclosed herein relate to systems, devices (e.g., wearabledevices, hardware storage devices, etc.), and methods that update aposition of overlaid image content using inertial measurement unit (IMU)data to reflect subsequent changes in camera positions to minimizelatency effects. As used herein, a “system camera” refers to anintegrated camera that is a part of an HMD. An “external camera” is acamera that is detached from or that is separated from the HMD. Anexample of an external camera can be a camera mounted on a tool used bya user who is also wearing an HMD.

In some embodiments, a system camera and an external camera generateimages. These images are overlaid on one another and aligned to form anoverlaid image. Content from the external camera image is surrounded bya bounding element in the overlaid image. IMU data associated with boththe system camera and the external camera is obtained. Based on that IMUdata, the embodiments determine an amount of movement that the systemcamera and/or the external camera have moved since the images wereoriginally generated. Based on that movement, the embodiments shift thebounding element to a new position in the overlaid image.

Some embodiments predict where the bounding element will be located atsome point in the future to minimize latency effects. After the IMU datais obtained (as described above), some embodiments generate (e.g., basedon the IMU data) a prediction as to where the external camera will berelative to the system camera at a determined future point in time.Based on that prediction, the embodiments shift the bounding element toa new position in the overlaid image to reflect the predicted position.

Examples of Technical Benefits, Improvements, and Practical Applications

The following section outlines some example improvements and practicalapplications provided by the disclosed embodiments. It will beappreciated, however, that these are just examples only and that theembodiments are not limited to only these improvements.

As described earlier, challenges occur when aligning image content fromtwo different cameras. Further challenges occur when the resultingoverlaid image includes a visualization (e.g., a bounding element) whosefunction is to reflect the spatial relationship between the systemcamera and the external camera. Because the processing and renderingprocesses are not instantaneous, movement of the system camera and/orthe external camera can result in the bounding element experiences avisual lag. The disclosed embodiments solve this lagging issue byacquiring IMU data to correct the lagging effects. In doing so, theembodiments provide substantial improvements to the user's experiencewith the HMD. Furthermore, the embodiments improve the visual effectsprovided by the HMD and also provide a more accurate and robustvisualization in the form of a passthrough image. Accordingly, bypracticing the disclosed principles, improved passthrough images may begenerated.

Example MR Systems and HMDs

Attention will now be directed to FIG. 1 , which illustrates an exampleof a head-mounted device (HMD) 100. HMD 100 can be any type of MR system100A, including a VR system 100B or an AR system 100C. It should benoted that while a substantial portion of this disclosure is focused onthe use of an HMD, the embodiments are not limited to being practicedusing only an HMD. That is, any type of camera system can be used, evencamera systems entirely removed or separate from an HMD. As such, thedisclosed principles should be interpreted broadly to encompass any typeof camera use scenario. Some embodiments may even refrain from activelyusing a camera themselves and may simply use the data generated by acamera. For instance, some embodiments may at least be partiallypracticed in a cloud computing environment.

HMD 100 is shown as including scanning sensor(s) 105 (i.e. a type ofscanning or camera system), and HMD 100 can use the scanning sensor(s)105 to scan environments, map environments, capture environmental data,and/or generate any kind of images of the environment (e.g., bygenerating a 3D representation of the environment or by generating a“passthrough” visualization). Scanning sensor(s) 105 may comprise anynumber or any type of scanning devices, without limit.

In accordance with the disclosed embodiments, the HMD 100 may be used togenerate a passthrough visualizations of the user's environment. As usedherein, a “passthrough” visualization refers to a visualization thatreflects the perspective of the environment from the user's point ofview. To generate this passthrough visualization, the HMD 100 may useits scanning sensor(s) 105 to scan, map, or otherwise record itssurrounding environment, including any objects in the environment, andto pass that data on to the user to view. As will be described shortly,various transformations may be applied to the images prior to displayingthem to the user to ensure the displayed perspective matches the user'sexpected perspective.

To generate a passthrough image, the scanning sensor(s) 105 typicallyrely on its cameras (e.g., head tracking cameras, hand tracking cameras,depth cameras, or any other type of camera) to obtain one or more rawimages (aka “texture images”) of the environment. In addition togenerating passthrough images, these raw images may also be used todetermine depth data detailing the distance from the sensor to anyobjects captured by the raw images (e.g., a z-axis range ormeasurement). Once these raw images are obtained, then a depth map canbe computed from the depth data embedded or included within the rawimages (e.g., based on pixel disparities), and passthrough images can begenerated (e.g., one for each pupil) using the depth map for anyreprojections, if needed.

From the passthrough visualizations, a user will be able to perceivewhat is currently in his/her environment without having to remove orreposition the HMD 100. Furthermore, as will be described in more detaillater, the disclosed passthrough visualizations can also enhance theuser's ability to view objects within his/her environment (e.g., bydisplaying additional environmental conditions that may not have beendetectable by a human eye). As used herein, a so-called “overlaid image”can be a type of passthrough image.

It should be noted that while the majority of this disclosure focuses ongenerating “a” passthrough image, the embodiments actually generate aseparate passthrough image for each one of the user's eyes. That is, twopassthrough images are typically generated concurrently with oneanother. Therefore, while frequent reference is made to generating whatseems to be a single passthrough image, the embodiments are actuallyable to simultaneously generate multiple passthrough images.

In some embodiments, scanning sensor(s) 105 include visible lightcamera(s) 110, low light camera(s) 115, thermal imaging camera(s) 120,potentially (though not necessarily, as represented by the dotted box inFIG. 1 ) ultraviolet (UV) camera(s) 125, potentially (though notnecessarily, as represented by the dotted box) a dot illuminator 130,and even an infrared camera 135. The ellipsis 140 demonstrates how anyother type of camera or camera system (e.g., depth cameras, time offlight cameras, virtual cameras, depth lasers, etc.) may be includedamong the scanning sensor(s) 105.

As an example, a camera structured to detect mid-infrared wavelengthsmay be included within the scanning sensor(s) 105. As another example,any number of virtual cameras that are reprojected from an actual cameramay be included among the scanning sensor(s) 105 and may be used togenerate a stereo pair of images. In this manner, the scanning sensor(s)105 may be used to generate the stereo pair of images. In some cases,the stereo pair of images may be obtained or generated as a result ofperforming any one or more of the following operations: active stereoimage generation via use of two cameras and one dot illuminator (e.g.,dot illuminator 130); passive stereo image generation via use of twocameras; image generation using structured light via use of one actualcamera, one virtual camera, and one dot illuminator (e.g., dotilluminator 130); or image generation using a time of flight (TOF)sensor in which a baseline is present between a depth laser and acorresponding camera and in which a field of view (FOV) of thecorresponding camera is offset relative to a field of illumination ofthe depth laser.

The visible light camera(s) 110 are typically stereoscopic cameras,meaning that the fields of view of the two or more visible light camerasat least partially overlap with one another. With this overlappingregion, images generated by the visible light camera(s) 110 can be usedto identify disparities between certain pixels that commonly representan object captured by both images. Based on these pixel disparities, theembodiments are able to determine depths for objects located within theoverlapping region (i.e. “stereoscopic depth matching” or “stereo depthmatching”). As such, the visible light camera(s) 110 can be used to notonly generate passthrough visualizations, but they can also be used todetermine object depth. In some embodiments, the visible light camera(s)110 can capture both visible light and IR light.

It should be noted that any number of cameras may be provided on the HMD100 for each of the different camera types (aka modalities). That is,the visible light camera(s) 110 may include 1, 2, 3, 4, 5, 6, 7, 8, 9,10, or more than 10 cameras. Often, however, the number of cameras is atleast 2 so the HMD 100 can perform passthrough image generation and/orstereoscopic depth matching, as described earlier. Similarly, the lowlight camera(s) 115, the thermal imaging camera(s) 120, and the UVcamera(s) 125 may each respectively include 1, 2, 3, 4, 5, 6, 7, 8, 9,10, or more than 10 corresponding cameras.

FIG. 2 illustrates an example HMD 200, which is representative of theHMD 100 from FIG. 1 . HMD 200 is shown as including multiple differentcameras, including cameras 205, 210, 215, 220, and 225. Cameras 205-225are representative of any number or combination of the visible lightcamera(s) 110, the low light camera(s) 115, the thermal imagingcamera(s) 120, and the UV camera(s) 125 from FIG. 1 . While only 5cameras are illustrated in FIG. 2 , HMD 200 may include more or lessthan 5 cameras.

In some cases, the cameras can be located at specific positions on theHMD 200. In some cases, a first camera (e.g., perhaps camera 220) isdisposed on the HMD 200 at a position above a designated left eyeposition of a user who wears the HMD 200 relative to a height directionof the HMD. For example, the camera 220 is positioned above the pupil230. As another example, the first camera (e.g., camera 220) isadditionally positioned above the designated left eye position relativeto a width direction of the HMD. That is, the camera 220 is positionednot only above the pupil 230 but also in-line relative to the pupil 230.When a VR system is used, a camera may be placed directly in front ofthe designated left eye position. With reference to FIG. 2 , a cameramay be physically disposed on the HMD 200 at a position in front of thepupil 230 in the z-axis direction.

When a second camera is provided (e.g., perhaps camera 210), the secondcamera may be disposed on the HMD 200 at a position above a designatedright eye position of a user who wears the HMD relative to the heightdirection of the HMD. For example, the camera 210 is above the pupil235. In some cases, the second camera is additionally positioned abovethe designated right eye position relative to the width direction of theHMD. When a VR system is used, a camera may be placed directly in frontof the designated right eye position. With reference to FIG. 2 , acamera may be physically disposed on the HMD 200 at a position in frontof the pupil 235 in the z-axis direction.

When a user wears HMD 200, HMD 200 fits over the user's head and the HMD200's display is positioned in front of the user's pupils, such as pupil230 and pupil 235. Often, the cameras 205-225 will be physically offsetsome distance from the user's pupils 230 and 235. For instance, theremay be a vertical offset in the HMD height direction (i.e. the “Y”axis), as shown by offset 240. Similarly, there may be a horizontaloffset in the HMD width direction (i.e. the “X” axis), as shown byoffset 245.

HMD 200 is configured to provide passthrough image(s) 250 for the userof HMD 200 to view. In doing so, HMD 200 is able to provide avisualization of the real world without requiring the user to remove orreposition HMD 200. These passthrough image(s) 250 effectively representthe view of the environment from the HMD's perspective. Cameras 205-225are used to provide these passthrough image(s) 250. The offset (e.g.,offset 240 and 245) between the cameras and the user's pupils results inparallax. In order to provide these passthrough image(s) 250, theembodiments can perform parallax correction by applying varioustransformations and reprojections on the images in order to change theinitial perspective represented by an image into a perspective matchesthat of the user's pupils. Parallax correction relies on the use of adepth map in order to make the reprojections.

In some implementations, the embodiments utilize a planar reprojectionprocess to correct parallax when generating the passthrough images asopposed to performing a full three-dimensional reprojection. Using thisplanar reprojection process is acceptable when objects in theenvironment are sufficiently far away from the HMD. Thus, in some cases,the embodiments are able to refrain from performing three-dimensionalparallax correction because the objects in the environment aresufficiently far away and because that distance results in a negligibleerror with regard to depth visualizations or parallax issues.

Any of the cameras 205-225 constitute what is referred to as a “systemcamera” because they are integrated parts of the HMD 200. In contrast,the external camera 255 is physically separate and detached from the HMD200 but can communicate wirelessly with the HMD 200. As will bedescribed shortly, it is desirable to align images (or image content)generated by the external camera 255 with images (or image content)generated by a system camera to then generate an overlaid image, whichcan operate as a passthrough image. Often, the angular resolution of theexternal camera 255 is higher (i.e. more pixels per degree and not justmore pixels) than the angular resolution of the system camera, so theresulting overlaid image provides enhanced image content beyond thatwhich is available from using only the system camera image.Additionally, or alternatively, the modalities of the external camera255 and the system camera may be different, so the resulting overlaidimage can also include enhanced information. As an example, suppose theexternal camera 255 is a thermal imaging camera. The resulting overlaidimage can, therefore, include visible light image content and thermalimage content. Accordingly, providing an overlaid passthrough image ishighly desirable. It should be noted that the external camera 255 may beany of the camera types listed earlier. Additionally, there may be anynumber of external cameras, without limit.

Example Scenarios

Attention will now be directed to FIG. 3 , which illustrates an examplescenario in which the HMDs discussed in FIGS. 1 and 2 may be used. FIG.3 shows a building 300 and a first responder 305 and another firstresponder 310. In this example scenario, the first responders 305 and310 are desirous to scale the building 300. FIG. 4 shows one exampletechnique for performing this scaling feat.

FIG. 4 shows a first responder wearing an HMD 400, which isrepresentative of the HMDs discussed thus far, in an environment 400A.HMD 400 includes a system camera 405, as discussed previously.Furthermore, the first responder is using a tool 410 that includes anexternal camera 415, which is representative of the external camera 255of FIG. 2 . In this case, the tool 410 is a grappling gun that will beused to shoot a rope and hook onto the building to allow the firstresponder to scale the building. By aligning the image content generatedby the external camera 415 with the image content generated by thesystem camera 405, the user will be able to better discern where thetool 410 is being aimed.

That is, in accordance with the disclosed principles, it is desirable toprovide an improved platform or technique by which a user (e.g., thefirst responders) can aim a tool (e.g., the tool 410) using the HMD 400,the system camera 405, and the external camera 415 as a combined aiminginterface. FIG. 5 shows one such example.

FIG. 5 shows a system camera 500 mounted on an HMD, where the systemcamera 500 is representative of the system camera 405 of FIG. 4 , and atool (e.g., a grappling gun) that includes an external camera 505, whichis representative of the external camera 415. It should be noted how theoptical axis of the external camera 505 is aligned with the aimingdirection of the tool. As a consequence, the images generated by theexternal camera 505 can be used to determine where the tool is beingaimed. One will appreciate how the tool can be any type of aimable tool,without limit.

In FIG. 5 , both the system camera 500 and the external camera 505 arebeing aimed at a target 510. To illustrate, the field of view (FOV) ofthe system camera 500 is represented by the system camera FOV 515, andthe FOV of the external camera 505 is represented by the external cameraFOV 520. Notice, the system camera FOV 515 is larger than the externalcamera FOV 520. Typically, the external camera 505 provides a veryfocused view, similar to that of a scope (i.e. a high level of angularresolution). As will be discussed in more detail later, the externalcamera 505 sacrifices a wide FOV for an increased resolution andincreased pixel density. Accordingly, in this example scenario, one canobserve how in at least some situations, the external camera FOV 520 maybe entirely overlapped or encompassed by the system camera FOV 515. Ofcourse, in the event the user aims the external camera 505 in adirection where the system camera 500 is not aimed at, then the systemcamera FOV 515 and the external camera FOV 520 will not overlap.

FIG. 6 shows the system camera FOV 600, which is representative of thesystem camera FOV 515 of FIG. 5 . The system camera FOV 600 will becaptured by the system camera in the form of a system camera image andwill potentially be displayed in the form of a passthrough image. Thesystem camera images have a resolution 605 and are captured by thesystem camera based on a determined refresh rate 610 of the systemcamera. The refresh rate 610 of the system camera is typically betweenabout 30 Hz and 120 Hz. Often, the refresh rate 610 is around 90 Hz orat least 60 Hz. Often, the system camera FOV 600 has at least a 55degree horizontal FOV. The horizontal baseline of the system camera FOV600 may extend to 65 degrees, or even beyond 65 degrees.

It should also be noted how the HMD includes an inertial measurementunit IMU 615. An IMU (e.g., IMU 615) is a type of device that measuresforces, angular rates, and orientations of a body. An IMU can use acombination of accelerometers, magnetometers, and gyroscopes to detectthese forces. Because both the system camera and the IMU 615 areintegrated with the HMD, the IMU 615 can be used to determine theorientation or pose of the system camera (and the HMD) as well as anyforces the system camera is being subjected to.

In some cases, the “pose” may include information detailing the 6degrees of freedom, or “6 DOF,” information. Generally, the 6 DOF poserefers to the movement or position of an object in three-dimensionalspace. The 6 DOF pose includes surge (i.e. forward and backward in thex-axis direction), heave (i.e. up and down in the z-axis direction), andsway (i.e. left and right in the y-axis direction). In this regard, 6DOF pose refers to the combination of 3 translations and 3 rotations.Any possible movement of a body can be expressed using the 6 DOF pose.

In some cases, the pose may include information detailing the 3 DOFpose. Generally, the 3 DOF pose refers to tracking rotational motiononly, such as pitch (i.e. the transverse axis), yaw (i.e. the normalaxis), and roll (i.e. the longitudinal axis). The 3 DOF pose allows theHMD to track rotational motion but not translational movement of itselfand of the system camera. As a further explanation, the 3 DOF poseallows the HMD to determine whether a user (who is wearing the HMD) islooking left or right, whether the user is rotating his/her head up ordown, or whether the user is pivoting left or right. In contrast to the6 DOF pose, when 3 DOF pose is used, the HMD is not able to determinewhether the user (or system camera) has moved in a translational manner,such as by moving to a new location in the environment.

Determining the 6 DOF pose and the 3 DOF pose can be performed usinginbuilt sensors, such as accelerometers, gyroscopes, and magnetometers(i.e. the IMU 615). Determining the 6 DOF pose can also be performedusing positional tracking sensors, such as head tracking sensors.Accordingly, the IMU 615 can be used to determine the pose of the HMD.

FIG. 7 shows an external camera FOV 700, which is representative of theexternal camera FOV 520 of FIG. 5 . Notice, the external camera FOV 700is smaller than the system camera FOV 600. That is, the angularresolution of the external camera FOV 700 is higher than the angularresolution of the system camera FOV 600. Having an increased angularresolution also results in the pixel density of an external camera imagebeing higher than the pixel density of a system camera image. Forinstance, the pixel density of an external camera image is often 2.5 to3 times that of the pixel density of a system camera image. As aconsequence, the resolution 705 of an external camera image is higherthan the resolution 605. Often, the external camera FOV 700 has at leasta 19 degree horizontal FOV. That horizontal baseline may be higher, suchas 20 degrees, 25 degrees, 30 degrees, or more than 30 degrees.

The external camera also has a refresh rate 710. The refresh rate 710 istypically lower than the refresh rate 610. For example, the refresh rate710 of the external camera is often between 20 Hz and 60 Hz. Typically,the refresh rate 710 is at least about 30 Hz. The refresh rate of thesystem camera is often different than the refresh rate of the externalcamera. In some cases, however, the two refresh rates may besubstantially the same.

The external camera also includes or is associated with an IMU 715.Using this IMU 715, the embodiments are able to detect or determine theorientation/pose of the external camera as well as any forces that theexternal camera is being subjected to. Accordingly, similar to theearlier discussion, the IMU 715 can be used to determine the pose (e.g.,6 DOF and/or 3 DOF) of the external camera sight.

In accordance with the disclosed principles, it is desirable to overlapand align the images obtained from the external camera with the imagesgenerated by the system camera to generate an overlaid and alignedpassthrough image. The overlap between the two images enables theembodiments to generate multiple images and then overlay image contentfrom one image onto another image in order to generate a composite imageor an overlaid image having enhanced features that would not be presentif only a single image were used. As one example, the system cameraimage provides a broad FOV while the external camera image provides highresolution and pixel density for a focused area (i.e. the aiming areawhere the tool is being aimed). By combining the two images, theresulting image will have the benefits of a broad FOV and a high pixeldensity for the aiming area.

It should be noted that while this disclosure primarily focuses on theuse of two images (e.g., the system camera image and the external cameraimage), the embodiments are able to align content from more than twoimages having overlapping regions. For instance, suppose 2, 3, 4, 5, 6,7, 8, 9, or even 10 integrated and/or detached cameras have overlappingFOVs. The embodiments are able to examine each resulting image and thenalign specific portions with one another. The resulting overlaid imagemay then be a composite image formed from any combination or alignmentof the available images (e.g., even 10 or more images, if available).Accordingly, the embodiments are able to utilize any number of imageswhen performing the disclosed operations and are not limited to only twoimages or two cameras.

As another example, suppose the system camera is a low light camera andfurther suppose the external camera is a thermal imaging camera. As willbe discussed in more detail later, the embodiments are able toselectively extract image content from the thermal imaging camera imageand overlay that image content onto the low light camera image. In thisregard, the thermal imaging content can be used to augment or supplementthe low light image content, thereby providing enhanced imagery to theuser. Additionally, because the external camera has increased resolutionrelative to the system camera, the resulting overlaid image will provideenhanced clarity for the areas where the pixels in the external cameraimage are overlaid onto the system camera image. FIG. 8 provides anexample of these operations and benefits.

Image Correspondences and Alignment

In accordance with the disclosed principles, the embodiments are able toalign the system camera's image with the external camera's image. Thatis, because at least a portion of the two cameras' FOVs overlap with oneanother, as was described earlier, at least a portion of the resultingimages include corresponding content. Consequently, that correspondingcontent can be identified and then a merged, fused, or overlaid imagecan be generated based on the similar corresponding content. Bygenerating this overlaid image, the embodiments are able to provideenhanced image content to the user, which enhanced image content wouldnot be available if only a single image type were provided to a user.Both the system camera's image and the external camera's images may bereferred to as “texture” images.

To merge or align the images, the embodiments are able to analyze thetexture images (e.g., perform computer vision feature detection) in anattempt to find any number of feature points. As used herein, the phrase“feature detection” generally refers to the process of computing imageabstractions and then determining whether an image feature (e.g., of aparticular type) is present at any particular point or pixel in theimage. Often, corners (e.g., the corners of a wall), distinguishableedges (e.g., the edge of a table), or ridges are used as feature pointsbecause of the inherent or sharp contrasting visualization of an edge orcorner.

Any type of feature detector may be programmed to identify featurepoints. In some cases, the feature detector may be a machine learningalgorithm. As used herein, reference to any type of machine learning mayinclude any type of machine learning algorithm or device, convolutionalneural network(s), multilayer neural network(s), recursive neuralnetwork(s), deep neural network(s), decision tree model(s) (e.g.,decision trees, random forests, and gradient boosted trees) linearregression model(s), logistic regression model(s), support vectormachine(s) (“SVM”), artificial intelligence device(s), or any other typeof intelligent computing system. Any amount of training data may be used(and perhaps later refined) to train the machine learning algorithm todynamically perform the disclosed operations.

In accordance with the disclosed principles, the embodiments detect anynumber of feature points (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30,40, 50, 60, 70, 80, 90, 100, 200, 500, 1,000, 2,000, or more than 2,000)and then attempt to identify correlations or correspondences between thefeature points detected in the system camera image and the featurepoints identified in the external camera image.

Some embodiments then fit the feature or image correspondence(s) to amotion model in order to overlay one image onto another image to form anenhanced overlaid image. Any type of motion model may be used.Generally, a motion model is a type of transformation matrix thatenables a model, a known scene, or an object to be projected onto adifferent model, scene, or object.

In some cases, the motion model may simply be a rotational motion model.With a rotational model, the embodiments are able to shift one image byany number of pixels (e.g., perhaps 5 pixels to the left and 10 pixelsup) in order to overlay one image onto another image. For instance, oncethe image correspondences are identified, the embodiments can identifythe pixel coordinates of those feature points or correspondences. Oncethe coordinates are identified, then the embodiments can overlay theexternal camera sight's image onto the HMD camera's image using therotational motion model approach described above.

In some cases, the motion model may be more complex, such as in the formof a similarity transform model. The similarity transform model may beconfigured to allow for (i) rotation of either one of the HMD camera'simage or the external camera sight's image, (ii) scaling of thoseimages, or (iii) homographic transformations of those images. In thisregard, the similarity transform model approach may be used to overlayimage content from one image onto another image. Accordingly, in somecases, the process of aligning the external camera image with the systemcamera image is performed by (i) identifying image correspondencesbetween the images and then, (ii) based on the identified imagecorrespondences, fitting the correspondences to a motion model such thatthe external camera image is projected onto the system camera image.

Another technique for aligning images includes using IMU data to predictposes of the system camera and the external camera. Once the two posesare estimated or determined, the embodiments then use those poses toalign one or more portions of the images with one another. Once aligned,then one or more portions of one image (which portions are the alignedportions) are overlaid onto the corresponding portions of the otherimage in order to generate an enhanced overlaid image. In this regard,IMUs can be used to determine poses of the corresponding cameras, andthose poses can then be used to perform the alignment processes.

FIG. 8 shows a resulting overlaid image 800 comprising portions (or all)of a system camera image 805 (i.e. an image generated by the systemcamera) and an external camera image 810 (i.e. an image generated by theexternal camera). Optionally, additional image artifacts can be includedin the overlaid image 800, such as perhaps a reticle 815 used to helpthe user aim the tool. By aligning the image content, a user of the toolcan determine where the tool is being aimed without having to look downthe tool's sights. Instead, the user can discern where the tool is beingaimed by simply looking at the content displayed in his/her HMD.

Providing the enhanced overlaid image 800 allows for rapid targetacquisition, as shown by target acquisition 900 in FIG. 9 . That is, atarget can be acquired (i.e. the tool is accurately aimed at a desiredtarget) in a fast manner because the user no longer has to take time tolook through the tool's sights.

Improved Image Alignment in Response to Camera Movement

There is often latency or a time delay between when the overlaid imageis displayed and when the images used to generate the overlaid image aregenerated. This time delay results in a scenario where the user isviewing delayed data, which means the displayed reticle 815 in FIG. 8may not truly reflect the actual aiming position of the tool. What isneeded, therefore, is an improved technique to compensate for delaysthat occur between image generation and image display. The remainingfigures will describe a technique for addressing such issues.

FIG. 10 shows an abstracted version of the images discussed thus far. Inparticular, FIG. 10 shows a system camera image 1000 and an externalcamera image 1005. As discussed, it is desirable to generate an overlaidimage 1010 comprising portions extracted or obtained from the systemcamera image 1000 and portions extracted or obtained from the externalcamera image 1005. Notice, in some embodiments, the overlaid image 1010includes a bounding element 1015 encompassing pixels that are obtainedfrom the external camera image 1005 and/or from the system camera image1000. Optionally, the bounding element 1015 may be in the form of acircular bubble visualization 1020. Other shapes may be used for thebounding element 1015, however.

FIG. 11 shows an overlaid image 1100, which is representative of theoverlaid image 1010 of FIG. 10 , and a bounding element 1105, which isrepresentative of the bounding element 1015. Here, movement 1110 is alsoillustrated. Movement 1110 may correspond to a movement of the systemcamera, as shown by system camera movement 1115, and/or movement of theexternal camera, as shown by the external camera movement 1120. Asdiscussed previously, there may be a time delay between when theoverlaid image 1100 is generated and displayed and when the systemcamera image and the external camera image are generated. During thistime period, if the movement 1110 occurs, then the resulting overlaidimage 1100 will no longer be up-to-date in that it will reflect a pastscenario (i.e. the location of the bounding element 1105 will be in thewrong position). FIG. 12 provides additional clarification.

FIG. 12 shows the traditional solution (lagging) 1200 where the boundingelement is displayed at a lagging position 1205 that does not reflectthe movement 1110 of FIG. 11 . Such an image is not desirable to displayto a user.

In contrast, the desired solution (up to date) 1210 shows the boundingelement in a correct position 1215 to account for the movement 1110 ofFIG. 11 . Such an image is desirable to display to the user.

FIG. 13 shows a scenario where the bounding element is originally in alagging position (incorrect position) 1300, but how the bounding elementcan be shifted (as shown by shift 1305) to a shifted position (correctposition) 1310. To perform this shift, the embodiments rely on IMU data1315, which includes IMU data from the IMUs associated with the systemcamera and the external camera. Generally, acquiring image data andmanipulating that image data (e.g., by performing a reprojection) takesa relatively longer amount of time as compared to manipulating databased on IMU data. With that understanding, then, the embodimentsselectively move the bounding element to a new position based on updatedIMU data that is obtained after the original system camera image andexternal camera image are generated.

Moving the bounding element (including, perhaps, moving the reticle)enables the embodiments to display an updated positional relationshipbetween the system camera and the external camera without having toacquire new image content to determine that updated position; instead,the IMU data is used to determine the updated positions (which occur asa result of movement). Therefore, the embodiments are able todynamically shift the bounding element to reflect any movements thathave occurred since the time when the system camera image and theexternal camera image were originally generated. It should be noted,only the bounding element is being moved; the external camera image isnot being realigned or reprojected. Further details on this aspect willbe provided later.

Example Methods

The following discussion now refers to a number of methods and methodacts that may be performed. Although the method acts may be discussed ina certain order or illustrated in a flow chart as occurring in aparticular order, no particular ordering is required unless specificallystated, or required because an act is dependent on another act beingcompleted prior to the act being performed.

Attention will now be directed to FIGS. 14A and 14B, which illustrate aflowchart of an example method 1400 for updating a position of overlaidimage content using IMU data to reflect subsequent changes in camerapositions in order to minimize latency effects. Method 1400 may beperformed using the HMDs, system cameras, and external cameras mentionedthus far.

Initially, method 1400 includes an act (act 1405) of using a systemcamera (e.g., system camera 405 of FIG. 4 ) of a head-mountedmixed-reality system (e.g., HMD 400) to generate a system camera image(e.g., system camera image 1000 of FIG. 10 ) of an environment (e.g.,environment 400A in FIG. 4 ) in which the system is operating. Inparallel with act 1405, method 1400 includes an act (act 1410) ofcausing an external camera (e.g., external camera 415 of FIG. 4 ) togenerate an external camera image (e.g., external camera image 1005 ofFIG. 10 ) of the environment. Notably, a FOV of the system cameraoverlaps a FOV of the external camera. As a consequence, contentincluded in the external camera image is also included in the systemcamera image. The system camera and the external camera can be one ormore of a visible light camera, a low light camera, or a thermal imagingcamera, among others.

Act 1415 then involves generating an overlaid image (e.g., overlaidimage 1010 of FIG. 10 ) by overlaying and aligning at least some of thecontent included in the external camera image on top of correspondingcontent included in the system camera image. Here, the overlaid contentpulled from the external camera image is surrounded by a boundingelement (e.g., bounding element 1015 in FIG. 10 ), as was discussedearlier. FIG. 15 provides additional context regarding method acts1405-1415.

FIG. 15 shows how an overlaid image 1500 can be generated by merging andaligning content from a system camera image and an external camera imagein the manner discussed previously. Notice, the overlaid image 1500includes pixels from both the system camera image (e.g., system cameraimage pixels 1505) and the external camera image (e.g., external cameraimage pixels 1510—the darkened areas). Also, notice how the externalcamera image pixels 1510 are encompassed by a bounding element (notlabeled, but evident from the illustration). The overlaid image 1500corresponds to the overlaid image mentioned in act 1415 of method 1400.

Returning to FIG. 14A, method 1400 further includes an act (act 1420) ofobtaining system IMU data from an IMU of the system. By way of example,the embodiments are able to obtain IMU data from the IMU 615 associatedwith the HMD and the system camera.

In parallel with act 1420, there is an act (act 1425) of obtainingexternal IMU data from an IMU of the external camera. By way of example,the embodiments are able to obtain IMU data from the IMU 715 associatedwith the external camera.

In FIG. 14B, method 1400 the lists a number of additional acts.Specifically, based on the system IMU data and the external IMU data,there is an act (act 1430) of determining an amount of movement that thesystem camera and/or the external camera have moved relative to oneanother since a time when the system camera image and the externalcamera image were generated.

Based on the determined amount of movement, there is then an act (act1435) of shifting the bounding element to a new position in the overlaidimage. As a consequence, the shifted bounding element reflects anupdated positional relationship between the FOV of the system camera andthe FOV of the external camera since the time when the system cameraimage and the external camera image were generated. FIG. 15 alsoillustrates this shifting effect.

FIG. 15 shows a modified image 1515, which is representative of theoverlaid image described in method act 1435. Here, the bounding elementhas been moved or shifted to a shifted position 1520. Notice, themodified image 1515 includes pixels obtained from the external cameraimage, as shown by external camera image pixels 1525, and pixelsobtained from the system camera image, as shown by the system cameraimage pixels 1530.

Notably, it is normally the case that pixels encompassed by the boundingelement belonged to or were obtained from the external camera image. Byway of additional clarification, prior to shifting the bounding element(e.g., prior to act 1435), pixels bounded by the bounding elementinclude pixels obtained only from the external camera image. FIG. 15shows how the overlaid image 1500 includes a bounding element and howthe pixels included in the bounding element (e.g., external camera imagepixels 1510) were obtained only from the external image.

If only pixels obtained from the external camera image were allowed tobe included in the bounding element, then the resulting modified image1515 would have missing pixels 1535. In order words, because only theexternal camera image pixels 1510 were originally available and becausethe shift caused the bounding element to be shifted to a new position,pixels would be lost, as shown by the missing pixels 1535. Such ascenario is not desirable. As such, the embodiments “fill in” certainareas encompassed by the bounding element with pixels obtained from thesystem camera image in an effort to ensure that the area surrounded bythe bounding element is fully represented without missing content. FIG.16 shows an example of this operation.

FIG. 16 shows how the bounding element 1600 now encompasses pixels thatare obtained from both the system camera image and the external cameraimage. To illustrate, notice how the bounding element 1600 bounds orencompasses external camera image pixels 1605, system camera imagepixels 1610, and system camera image pixels 1615. Previously (e.g., inthe overlaid image generated in method act 1415), the bounding element1600 encompassed pixels obtained only from the external camera. Thepixels obtained from the external camera were shown by the externalcamera image pixels 1510 in FIG. 15 (i.e. the darkened areas).

When the bounding element is shifted to a new position (e.g., moved tothe left in this case), the external camera image pixels 1605 are theonly pixels from the external camera image that remain within thebounding element 1600. Suppose a constraint were imposed where thebounding element 1600 was allowed to encompass only pixels obtained fromthe external camera image. If that were the case, then only the portionof the star shown in FIG. 15 (i.e. the external camera image pixels1525) would be displayed, and the right portion of the plus sign wouldbe missing, as shown by the missing pixels 1535. To avoid such ascenario, the embodiments refrain from implementing the above-describedconstraint and instead allow the bounding element to encompass pixelsthat are obtained from sources other than just the external cameraimage. In essence, pixels can be “filled in” using the system cameraimage to provide a complete view within the bounding element 1600.

To illustrate, the system camera image pixels 1610 and 1615, which arepixels obtained from the system camera image, can be used to fill in theareas that would not have been filled in if the above-describedconstraint were imposed.

By way of additional clarification, the process of shifting the boundingelement to the new position in the overlaid image may include a numberof steps. One step involves identifying pixels included within theexternal camera image. Another step involves determining that, as aresult of shifting the bounding element to the new position, some, butnot all, image content that is now to be included within the shiftedbounding element are not representable by the identified pixels includedwithin the external camera image. For instance, the embodiments identifya scenario where pixels are missing (e.g. the missing pixels 1535 inFIG. 15 ).

Then, for the some, but not all, image content that is now to beincluded in the shifted bounding element and that is not representableby the identified pixels included within the external camera image, theembodiments selectively use pixels from the system camera image (e.g.,system camera image pixels 1610 and 1615 in FIG. 16 ) to display thatimage content. As a consequence, the shifted bounding element boundspixels originating from the system camera image and pixels originatingfrom the external camera image.

It should be noted that shifting the bounding element to the newposition does not trigger the reprojection of image content or pixels.That is, the original alignment between the system camera image and theexternal camera image remains intact; only the position of the boundingelement has changed. FIG. 17 provides clarification regarding thisconcept.

FIG. 17 shows an original overlaid image 1700, which is representativeof the overlaid image discussed in method act 1415 of FIG. 14A. As aresult of performing the other operations recited in method 1400, thebounding element is shifted to a new position, as reflected by theshifted bounding element 1705 in the modified overlaid image 1710.

In FIG. 17 , the black pixels correspond to pixels obtained from theexternal camera image. Notice, even though the bounding element hasshifted to a new position, the original alignment between the externalcamera image and the system camera image is preserved, as shown by thepreserved alignment 1715. What this means is that in someimplementations, high resolution pixels will be displayed in areasoutside of the shifted bounding element 1705.

Notably, the previous bounding element 1720 reflects the originalposition of the bounding element before being shifted. When the modifiedoverlaid image 1710 is displayed, the previous bounding element 1720will not be displayed; instead, the shifted bounding element 1705 willbe displayed. In this regard, only the bounding element is shifted, andthe content included in the external camera image is not shifted suchthat the external camera image remains overlaid on and aligned with thesystem camera image despite the bounding element being shifted to a newposition.

To reiterate, it should be noted that the pixels obtained from theexternal camera image (i.e. the darkened areas in FIG. 17 ), even thosethat are not currently encompassed by the shifted bounding element 1705(e.g., those dark pixels in the minus sign), can still be displayed. Notbeing encompassed in the shifted bounding element 1705 will not preventthose pixels from being displayed. As such, the embodiments preserve theoriginal alignment of the external camera image and the system cameraimage and focus on shifting only the bounding element in response todetected movements, which are detected and measured using IMU dataobtained from the IMUs associated with the system camera and theexternal camera.

Recall, the pixel density and resolution of the external camera image isoften higher than the pixel density and resolution of the system cameraimage. As a result of performing the disclosed operations, it is oftenthe case that the bounding element will encompass pixels havingdifferent resolutions and densities. FIG. 18 shows such a scenario.

FIG. 18 shows how the bounding element (and now other portions of theoverlaid image) can include or encompass higher resolution pixels 1800(i.e. the darkened areas), which are obtained from the external cameraimage, and lower resolution pixels 1805 and 1810 (i.e. thediagonally-lined areas), which are obtained from the system cameraimage. As a result of performing the shifting operations, theembodiments in essence sacrifice pixel resolution 1815 within thebounding element for increased update speed 1820 of the bounding element(i.e. the speed by which the accurate position of the bounding elementis displayed).

By way of additional clarification, the pixels that originated from thesystem camera image and that are bounded by the shifted bounding element(e.g., lower resolution pixels 1805 and 1810) are lower in resolutionthan the pixels that originated from the external camera image and thatare bounded by the shifted bounding element (e.g., higher resolutionpixels 1800). Stated differently, as a result of shifting the boundingelement, pixels bounded by the bounding element include lower resolutionpixels obtained from the system camera image and higher resolutionpixels obtained from the external camera image such that shifting thebounding element sacrifices pixel resolution within the bounding elementfor update speed of the bounding element.

In some cases, the bounding element may not encompass any pixelsobtained from the external camera image. FIG. 19 is representative.

FIG. 19 shows a bounding element 1900 and system camera image pixels1905, 1910, 1915, and 1920. Notice, in this example, there are no pixelsoriginating from the external camera image. It may be the case that thesystem camera and/or external camera have moved so much and so quicklythat the shift to the bounding element 1900 results in no pixels fromthe external camera image being bounded by the bounding element 1900.Additionally, or alternatively, it may be the case that it is desirableto not display (at least temporarily) pixels originating from theexternal camera image.

By way of example, suppose the external camera is a thermal imagingcamera and suppose the system camera is a visible light camera. Furthersuppose the system camera and the external camera are being used in adaylight environment. In such an environment, it may be beneficial todisplay pixels obtained only from the visible light camera image andrefrain from displaying pixels obtained from the thermal imaging cameraimage because the user may not need enhanced thermal imaging data inthat daylight environment. Instead, it may be desirable to display onlythe bounding element 1900 at the correct and accurate location. As such,some embodiments may selectively filter pixels or selectively refrainfrom displaying pixels originating from the external camera image andmay instead display the bounding element 1900. Accordingly, FIG. 19represents a scenario where pixels bounded by the shifted boundingelement include pixels obtained only from the system camera image suchthat no pixels from the external camera image are bounded by the shiftedbounding element.

The direction of movement of the system camera and the external cameracan also play a role in which pixels will be encompassed by the shiftedbounding element. For example, it is typically the case that the imagegenerated by the external camera is in the form of a rectangle, wherethe horizontal base is larger than the vertical height. Consequently,there will be differences that occur depending on which direction thesystem camera and/or the external camera are moving. FIG. 20 isrepresentative.

FIG. 20 shows the rectangular external camera image 2000 and theoriginal position 2005 of the bounding element. FIG. 20 also shows ascenario in which horizontal movement 2010 is occurring. As a result ofthe horizontal movement 2010, the embodiments shift the bounding elementto a new position, as shown by the shifted bounding element 2015.Because of the rectangular dimension of the external camera image 2000,the bounding element can shift a larger amount and still encompasspixels originating from the external camera image 2000 as compared to ascenario where a vertical movement is occurring. To illustrate, only asmall sliver of pixels, as shown by system camera image pixels 2020,will be used to fill in the area of the shifted bounding element 2015extending beyond the external camera image 2000. In this regard, farthermovements in the horizontal direction can be made before system cameraimage pixels begin to be bounded by the bounding element.

Now, consider the external camera image 2025, the original position 2030of the bounding element, and the vertical movement 2035. Because theheight of the rectangular external camera image 2025 is smaller than thewidth of the rectangle, vertical movements will likely result in morepixels originating from the system camera image being bounded by theshifted bounding element 2040. For example, a large area of pixels, asshown by system camera image pixels 2045, will be pulled in or used forthis example scenario. Accordingly, a direction of movement of one orboth of the system camera and the external camera (as well as a speed ofthat movement) will result in differences between how many system cameraimage pixels will be encompassed within the shifted bounding element.

FIG. 21 illustrates an example timeline that is useful for outlining thetiming of the operations. At time T₀, the embodiments trigger thegeneration of the system camera image and the external camera image, asshown by generate image(s) 2100. At time T₁, the embodiments generatethe initial overlaid image, as shown by generate overlaid image 2105. Attime T₂, the embodiments obtain IMU data 2110 from the IMUs associatedwith the system camera and the external camera. Notice, the IMU data isreceived or obtained after the overlaid image is generated.

At time T₃, the embodiments determine movement 2115 has occurred betweenthe system camera and the external camera by analyzing the IMU data. Insome cases, the time when the system camera image and the externalcamera image were generated (i.e. time T₀) to the time when the amountof movement is determined via the IMU data (i.e. time T₃) is at least 5milliseconds (ms). Sometimes, the time is at least 10 ms, 15 ms, 20 ms,or more than 20 ms.

At time T₄, the embodiments shift the bounding element 2120 based on theIMU data. Optionally, and as will be discussed shortly, the embodimentsmay shift the bounding element to a future point in time 2125 that isnot currently represented by the IMU data but that is a predictedlocation. Further details on this feature will be provided later. Pixelsbounded by the shifted bounding element at time T₄ include pixelsoriginating from the system camera image and pixels originating from theexternal camera image. Furthermore, as a time difference between time T₀and time T₄ increases, a number of pixels originating from the systemcamera image increases within the shifted bounding element while anumber of pixels originating from the external camera image decreaseswithin the shifted bounding element.

At time T₅, the embodiments display 2130 the overlaid image with theshifted bounding element. It should be noted that at any time betweentime T₀ and T₅, movement 2135 of the system camera and/or the externalcamera may occur. It is because of this movement 2135 that theembodiments shift the bounding element in an attempt to provide anaccurate illustration regarding the location of the system camerarelative to the external camera.

Predictions Regarding Future Location

As illustrated by the timeline of FIG. 21 , it may be the case thatmovement occurs even after the bounding element is shifted and beforethe overlaid image is displayed. With such scenarios, latency may stillbe observable, thereby detracting the user's experience. Therefore, someembodiments generate a prediction regarding future locations of thesystem camera and the external camera and then shift the boundingelement to reflect these predicted locations in an attempt to avoid alllatency effects. FIG. 22 illustrates a flowchart of an example method2200 for predicting where a bounding element should be located within anoverlaid image using IMU data and for minimizing latency effects. Itshould be noted that the first few acts of method 2200 are the same asthe first few acts of method 1400 in FIG. 14A. Specifically, method acts1405, 1410, 1415, 1420, and 1425 are also included in method 2200 andthus are not repeated in FIG. 22 .

Accordingly, act 2205 of method 2200 is triggered after act 1425. Thatis, based on the system IMU data and the external IMU data, act 2205involves generating a prediction indicating a predicted relativeposition that the external camera will be relative to the system cameraat a determined future point in time. This predicted point in time maybe 5 milliseconds (ms) after the system camera image and the externalcamera image are generated (e.g., time T₀ in FIG. 21 ), 6 ms after timeT₀, 7 ms after, 8 ms after, 9 ms after, 10 ms after, or more than 10 msafter time T₀. By way of example, the embodiments are able to analyzethe received IMU data to predict the future locations and poses of thesystem camera and external camera. That prediction can then be used todetermine where and how to shift the bounding element.

Specifically, based on the prediction, act 2210 includes shifting thebounding element to a new position in the overlaid image in order toreflect the predicted relative position of the external camera relativeto the system camera. By generating this prediction, which reflects anestimated or predicted location of the system camera and external cameraat some future point in time, the embodiments can entirely eliminate theeffects of latency.

The prediction is based on the IMU data. For example, based on the IMUdata, the embodiments can identify how the system camera and externalcamera are currently moving and can use that information to infer orpredict where, when, and how the system camera and the external camerawill continue to move.

Accordingly, the disclosed embodiments are able to dynamically shift abounding element in an effort to reflect an accurate spatialrelationship between a system camera and an external camera. Althoughpixel resolution within the bounding element may be reduced as a resultof this shift, the embodiments improve the accuracy by which thebounding element is displayed. The improved pixel resolution will followwith subsequent image captures by the system camera and the externalcamera. As such, the reduced pixel resolution within the boundingelement will be observable for only a very short period of time, whichis dependent on the refresh rates of the system camera and the externalcamera. Once new images are generated, then the pixel resolution withinthe bounding element will return to its high quality state. During rapidmovement events, however, accurate placement of the bounding element(e.g., the reticle) is given more weight or is assigned a higherpriority over the pixel resolution (during that short period of time).Accordingly, substantial benefits may be achieved by practicing thedisclosed principles.

Example Computer/Computer Systems

Attention will now be directed to FIG. 23 which illustrates an examplecomputer system 2300 that may include and/or be used to perform any ofthe operations described herein. Computer system 2300 may take variousdifferent forms. For example, computer system 2300 may be embodied as atablet 2300A, a desktop or laptop 2300B, a wearable HMD 2300C, a mobiledevice, or any other type of standalone device, as represented by theellipsis 2300D. Computer system 2300 may also be a distributed systemthat includes one or more connected computing components/devices thatare in communication with computer system 2300.

In its most basic configuration, computer system 2300 includes variousdifferent components. FIG. 23 shows that computer system 2300 includesone or more processor(s) 2305 (aka a “hardware processing unit”) andstorage 2310. As discussed previously, the computer system 2300 may alsoinclude any number or type of cameras.

Regarding the processor(s) 2305, it will be appreciated that thefunctionality described herein can be performed, at least in part, byone or more hardware logic components (e.g., the processor(s) 2305). Forexample, and without limitation, illustrative types of hardware logiccomponents/processors that can be used include Field-Programmable GateArrays (“FPGA”), Program-Specific or Application-Specific IntegratedCircuits (“ASIC”), Program-Specific Standard Products (“ASSP”),System-On-A-Chip Systems (“SOC”), Complex Programmable Logic Devices(“CPLD”), Central Processing Units (“CPU”), Graphical Processing Units(“GPU”), or any other type of programmable hardware.

Storage 2310 may be physical system memory, which may be volatile,non-volatile, or some combination of the two. The term “memory” may alsobe used herein to refer to non-volatile mass storage such as physicalstorage media. If computer system 2300 is distributed, the processing,memory, and/or storage capability may be distributed as well.

Storage 2310 is shown as including executable instructions (i.e. code2315). The executable instructions represent instructions that areexecutable by the processor(s) 2305 of computer system 2300 to performthe disclosed operations, such as those described in the variousmethods.

The disclosed embodiments may comprise or utilize a special-purpose orgeneral-purpose computer including computer hardware, such as, forexample, one or more processors (such as processor(s) 2305) and systemmemory (such as storage 2310), as discussed in greater detail below.Embodiments also include physical and other computer-readable media forcarrying or storing computer-executable instructions and/or datastructures. Such computer-readable media can be any available media thatcan be accessed by a general-purpose or special-purpose computer system.Computer-readable media that store computer-executable instructions inthe form of data are “physical computer storage media” or a “hardwarestorage device.” Computer-readable media that carry computer-executableinstructions are “transmission media.” Thus, by way of example and notlimitation, the current embodiments can comprise at least two distinctlydifferent kinds of computer-readable media: computer storage media andtransmission media.

Computer storage media (aka “hardware storage device”) arecomputer-readable hardware storage devices, such as RAM, ROM, EEPROM,CD-ROM, solid state drives (“SSD”) that are based on RAM, Flash memory,phase-change memory (“PCM”), or other types of memory, or other opticaldisk storage, magnetic disk storage or other magnetic storage devices,or any other medium that can be used to store desired program code meansin the form of computer-executable instructions, data, or datastructures and that can be accessed by a general-purpose orspecial-purpose computer.

Computer system 2300 may also be connected (via a wired or wirelessconnection) to external sensors (e.g., one or more remote cameras) ordevices via a network 2320. For example, computer system 2300 cancommunicate with any number devices (e.g., device 2325, such as anexternal camera) or cloud services to obtain or process data. In somecases, network 2320 may itself be a cloud network. Furthermore, computersystem 2300 may also be connected through one or more wired or wirelessnetworks 2320 to remote/separate computer systems(s) that are configuredto perform any of the processing described with regard to computersystem 2300.

A “network,” like network 2320, is defined as one or more data linksand/or data switches that enable the transport of electronic databetween computer systems, modules, and/or other electronic devices. Wheninformation is transferred, or provided, over a network (eitherhardwired, wireless, or a combination of hardwired and wireless) to acomputer, the computer properly views the connection as a transmissionmedium. Computer system 2300 will include one or more communicationchannels that are used to communicate with the network 2320.Transmissions media include a network that can be used to carry data ordesired program code means in the form of computer-executableinstructions or in the form of data structures. Further, thesecomputer-executable instructions can be accessed by a general-purpose orspecial-purpose computer. Combinations of the above should also beincluded within the scope of computer-readable media.

Upon reaching various computer system components, program code means inthe form of computer-executable instructions or data structures can betransferred automatically from transmission media to computer storagemedia (or vice versa). For example, computer-executable instructions ordata structures received over a network or data link can be buffered inRAM within a network interface module (e.g., a network interface card or“NIC”) and then eventually transferred to computer system RAM and/or toless volatile computer storage media at a computer system. Thus, itshould be understood that computer storage media can be included incomputer system components that also (or even primarily) utilizetransmission media.

Computer-executable (or computer-interpretable) instructions comprise,for example, instructions that cause a general-purpose computer,special-purpose computer, or special-purpose processing device toperform a certain function or group of functions. Thecomputer-executable instructions may be, for example, binaries,intermediate format instructions such as assembly language, or evensource code. Although the subject matter has been described in languagespecific to structural features and/or methodological acts, it is to beunderstood that the subject matter defined in the appended claims is notnecessarily limited to the described features or acts described above.Rather, the described features and acts are disclosed as example formsof implementing the claims.

Those skilled in the art will appreciate that the embodiments may bepracticed in network computing environments with many types of computersystem configurations, including personal computers, desktop computers,laptop computers, message processors, hand-held devices, multi-processorsystems, microprocessor-based or programmable consumer electronics,network PCs, minicomputers, mainframe computers, mobile telephones,PDAs, pagers, routers, switches, and the like. The embodiments may alsobe practiced in distributed system environments where local and remotecomputer systems that are linked (either by hardwired data links,wireless data links, or by a combination of hardwired and wireless datalinks) through a network each perform tasks (e.g. cloud computing, cloudservices and the like). In a distributed system environment, programmodules may be located in both local and remote memory storage devices.

The present invention may be embodied in other specific forms withoutdeparting from its characteristics. The described embodiments are to beconsidered in all respects only as illustrative and not restrictive. Thescope of the invention is, therefore, indicated by the appended claimsrather than by the foregoing description. All changes which come withinthe meaning and range of equivalency of the claims are to be embracedwithin their scope.

What is claimed is:
 1. A head-mounted mixed-reality system configured toupdate a position of overlaid image content using inertial measurementunit (IMU) data to reflect subsequent changes in camera positions and tominimize latency effects, said system comprising: one or moreprocessors; and one or more computer-readable hardware storage devicesthat store instructions that are executable by the one or moreprocessors to cause the system to at least: use a system camera of thehead-mounted mixed-reality system to generate a system camera image ofan environment in which the head-mounted mixed-reality system isoperating; cause an external camera to generate an external camera imageof the environment; generate an overlaid image by overlaying andaligning at least some of the content included in the external cameraimage on top of corresponding content included in the system cameraimage, wherein the at least some of the content included in the externalcamera image is surrounded by a bounding element; obtain system IMU datafrom an IMU of the head-mounted mixed-reality system; obtain externalIMU data from an IMU of the external camera; based on the system IMUdata and the external IMU data, determine an amount of movement that thesystem camera and/or the external camera have moved relative to oneanother since a time when the system camera image and the externalcamera image were generated; and based on the determined amount ofmovement, shift the bounding element to a new position in the overlaidimage such that the shifted bounding element reflects an updatedpositional relationship between a field of view (FOV) of the systemcamera and a FOV of the external camera since the time when the systemcamera image and the external camera image were generated.
 2. Thehead-mounted mixed-reality system of claim 1, wherein shifting thebounding element to the new position in the overlaid image includes:identifying pixels included within the external camera image;determining that, as a result of shifting the bounding element to thenew position, some, but not all, image content that is now to beincluded within the shifted bounding element are not representable bythe identified pixels included within the external camera image; and forthe some, but not all, image content that is now to be included in theshifted bounding element and that is not representable by the identifiedpixels included within the external camera image, selectively use pixelsfrom the system camera image to display the some, but not all, imagecontent such that the shifted bounding element bounds pixels originatingfrom the system camera image and pixels originating from the externalcamera image.
 3. The head-mounted mixed-reality system of claim 1,wherein the system camera and/or the external camera are one or more of:a visible light camera, a low light camera, an infrared camera, or athermal imaging camera.
 4. The head-mounted mixed-reality system ofclaim 1, wherein the bounding element includes a circular bubblevisualization.
 5. The head-mounted mixed-reality system of claim 1,wherein a refresh rate of the system camera is at least 60 Hz, andwherein a refresh rate of the external camera is at least 30 Hz.
 6. Thehead-mounted mixed-reality system of claim 1, wherein a refresh rate ofthe system camera is different than a refresh rate of the externalcamera.
 7. The head-mounted mixed-reality system of claim 1, wherein thetime when the system camera image and the external camera image weregenerated to a time when the amount of movement is determined is atleast 10 milliseconds.
 8. The head-mounted mixed-reality system of claim1, wherein the IMU data from the IMU of the head-mounted mixed-realitysystem and the IMU data from the IMU of the external camera are obtainedafter the overlaid image is generated.
 9. The head-mounted mixed-realitysystem of claim 1, wherein an angular image resolution provided by theexternal camera is higher than an angular resolution provided by thesystem camera.
 10. The head-mounted mixed-reality system of claim 1,wherein the FOV of the external camera is smaller than the FOV of thesystem camera.
 11. A method for updating a position of overlaid imagecontent using inertial measurement unit (IMU) data to reflect subsequentchanges in camera positions and to minimize latency effects, said methodcomprising: using a system camera of a mixed-reality system to generatea system camera image of an environment in which the mixed-realitysystem is operating; causing an external camera to generate an externalcamera image of the environment, wherein a field of view (FOV) of thesystem camera overlaps a FOV of the external camera such that contentincluded in the external camera image is also included in the systemcamera image; generating an overlaid image by overlaying and aligning atleast some of the content included in the external camera image on topof corresponding content included in the system camera image, whereinthe at least some of the content included in the external camera imageis surrounded by a bounding element; obtaining system IMU data from anIMU of the mixed-reality system; obtaining external IMU data from an IMUof the external camera; based on the system IMU data and the externalIMU data, determining an amount of movement that the system cameraand/or the external camera have moved relative to one another since atime when the system camera image and the external camera image weregenerated; and based on the determined amount of movement, shifting thebounding element to a new position in the overlaid image such that theshifted bounding element reflects an updated positional relationshipbetween the FOV of the system camera and the FOV of the external camerasince the time when the system camera image and the external cameraimage were generated.
 12. The method of claim 11, wherein shifting thebounding element to the new position in the overlaid image includes:identifying pixels included within the external camera image;determining that, as a result of shifting the bounding element to thenew position, some, but not all, image content that is now to beincluded within the shifted bounding element are not representable bythe identified pixels included within the external camera image; and forthe some, but not all, image content that is now to be included in theshifted bounding element and that is not representable by the identifiedpixels included within the external camera image, selectively use pixelsfrom the system camera image to display the some, but not all, imagecontent such that the shifted bounding element bounds pixels originatingfrom the system camera image and pixels originating from the externalcamera image.
 13. The method of claim 12, wherein the pixels thatoriginated from the system camera image and that are bounded by theshifted bounding element are lower in resolution than the pixels thatoriginated from the external camera image and that are bounded by theshifted bounding element.
 14. The method of claim 11, wherein pixelsbounded by the shifted bounding element include pixels obtained onlyfrom the system camera image such that no pixels from the externalcamera image are bounded by the shifted bounding element.
 15. The methodof claim 11, wherein, prior to shifting the bounding element, pixelsbounded by the bounding element include pixels obtained only from theexternal camera image.
 16. The method of claim 11, wherein only thebounding element is shifted and the content included in the externalcamera image is not shifted such that the external camera image remainsoverlaid on and aligned with the system camera image despite thebounding element being shifted.
 17. The method of claim 11, wherein, asa result of shifting the bounding element, pixels bounded by thebounding element include lower resolution pixels obtained from thesystem camera image and higher resolution pixels obtained from theexternal camera image such that shifting the bounding element sacrificespixel resolution within the bounding element for update speed of thebounding element.
 18. The method of claim 11, wherein: the time when thesystem camera image and the external camera image were generated is timeT₀, a time when the bounding element is shifted is time T₄, pixelsbounded by the shifted bounding element at time T₄ include pixelsoriginating from the system camera image and pixels originating from theexternal camera image, and as a time difference between time T₀ and timeT₄ increases, a number of pixels originating from the system cameraimage increases within the shifted bounding element while a number ofpixels originating from the external camera image decreases within theshifted bounding element.
 19. A system configured to predict where abounding element is to be located within an overlaid image usinginertial measurement unit (IMU) data and to minimize latency effects,said system comprising: one or more processors; and one or morecomputer-readable hardware storage devices that store instructions thatare executable by the one or more processors to cause the system to atleast: use a system camera of the system to generate a system cameraimage of an environment in which the system is operating; cause anexternal camera to generate an external camera image of the environment;generate an overlaid image by overlaying and aligning at least some ofthe content included in the external camera image on top ofcorresponding content included in the system camera image, wherein theat least some of the content included in the external camera image issurrounded by a bounding element; obtain system IMU data from an IMU ofthe system; obtain external IMU data from an IMU of the external camera;based on the system IMU data and the external IMU data, generate aprediction indicating a predicted relative position that the externalcamera will be relative to the system camera at a determined futurepoint in time; and based on said prediction, shift the bounding elementto a new position in the overlaid image to reflect the predictedrelative position of the external camera relative to the system camera.20. The system of claim 19, wherein generating the system camera imageand the external camera image is performed at time T₀, and wherein thedetermined future point in time is at least T₀+10 milliseconds.